Microelectronic devices are used in cell phones, pagers, personal digital assistants, computers, and many other products. One process for packaging microelectronic devices is wafer-level packaging. In wafer-level packaging, a plurality of microelectronic dies are formed on a wafer and a redistribution layer is formed over the dies. The redistribution layer includes a dielectric layer and a plurality of conductive lines in the dielectric layer that define ball-pad arrays. Each line has one end connected to a bond-pad on a die and another end connected to a ball-pad of an array. Each ball-pad array is arranged over a corresponding microelectronic die. After forming the redistribution layer on the wafer, a stenciling machine deposits discrete blocks of solder paste onto the ball-pads of the redistribution layer or balls are attached using ball-attach machines. The solder paste is then reflowed to form solder balls or solder bumps on the ball-pads. After forming the solder balls on the ball-pads, the wafer is cut to singulate the dies, and the individual dies can then undergo further processing.
Wafer-level packaging is a promising development for reducing the cost of manufacturing microelectronic devices. By “prepackaging” the individual dies with the redistribution layer before cutting the wafers to singulate the dies, sophisticated semiconductor processing techniques can be used to form smaller arrays of solder balls. Additionally, wafer-level packaging is an efficient process that simultaneously packages a plurality of dies to reduce costs, increase throughput, and increase performance.
One concern of wafer-level packaged microelectronic devices, however, is that the bare dies may be chipped or damaged during processing (e.g., backgrinding, dicing, plating, etc.) and/or post-processing handling. To help alleviate this problem, a protective film or cover can be placed over the front side and/or the back side of each wafer before processing. Currently, this protective film is a sheet of tape that is applied to each individual wafer before processing, and then subsequently removed from the individual wafers after processing.
Conventional processes for removing the sheet of tape from the workpiece generally include applying a removal or “detape” tape to the protective tape to help lift the protective tape off the workpiece. FIG. 1, for example, is a schematic cross-sectional view of a conventional system 10 for removing protective tape from a microfeature workpiece 12. The workpiece 12 includes a first side 14 and a second side 16 opposite the first side 14. The first side 14 is releasably attached to a layer of mounting tape 22 on a support member 20, and the second side 16 is generally covered by a protective tape 18. The system 10 includes a plurality of rollers to position, apply, and subsequently lift off a removal tape 30 from the workpiece 12. More specifically, in a previous processing step an application roller (not shown) applied the removal tape 30 onto at least a portion of the protective tape 18. After application of the removal tape 30, a take-up roller assembly 32 or the workpiece 12 moves such that the take-up roller assembly 32 progresses relative to the protective tape 18 (as shown by the arrow A) to lift or pull up the removal tape and corresponding portions of the protective tape 18 from the workpiece.
One drawback with this approach, however, is that the removal tape 30 must be placed precisely on the workpiece 12 and over the protective tape 18. For example, a leading edge 31 of the removal tape 30 must generally be positioned within about 0.5 mm of the edge of the workpiece 12 to be effective. If the removal tape 30 overhangs or is too close to the edge of the workpiece 12, the removal tape 30 can inadvertently adhere to the mounting tape 22 and lifting or pulling up on the removal tape can crack or otherwise damage the edge of the workpiece. On the other hand, if the leading edge 31 of the removal tape 30 is positioned too far inboard of the edge of the workpiece 12, the removal tape may not initiate removal of the edge of the protective tape 18.
FIG. 2 is a schematic cross-sectional view of another conventional system 40 for removing the protective tape 18 from the workpiece 12. In this system, the removal tape 30 is applied to the workpiece 12 and over desired portions of the protective tape 18 using a peel bar 50. More specifically, the peel bar 50 is positioned at a desired location relative to the edge of the workpiece 12 (e.g., within about 0.5 mm of the edge) and pressure is applied to the peel bar such that the bar applies a portion of the removal tape 30 to a desired portion of the protective tape 18. The workpiece 12 then moves relative to the peel bar 50 (as shown by the arrow B) and the removal tape 30 begins to lift up and remove the corresponding portions of the protective tape 18 on the workpiece 12.
This approach, however, also includes a number of drawbacks. For example, in situations where the workpiece 12 is extremely thin, the peel bar 50 must be precisely positioned relative to the edge of the workpiece to avoid cracking or otherwise damaging the workpiece. Furthermore, as with the system 10 described above with reference to FIG. 1, the leading edge of the removal tape 30 must be precisely positioned relative to the edge of the workpiece 12 in order to effectively remove the protective tape 18. If the peel bar 50 is positioned too close to the edge, it may overhang the workpiece 12 and inadvertently contact the mounting tape (as shown in broken lines), potentially cracking or breaking the edge of the workpiece. On the other hand, if the peel bar 50 is positioned too far inboard of the edge of the workpiece 12, the removal tape 30 may not have enough force to initiate removal of the edge of the protective tape 18 on the workpiece.
Yet another drawback with the system 40 is that it can be difficult to control the amount of force applied by the peel bar 50 to the workpiece 12. For example, after the peel bar 50 is precisely positioned at a desired location relative to the workpiece's edge, the peel bar must press against the workpiece 12 with a force sufficient to apply the removal tape 30 to the protective tape 18 and initiate the removal process. If the peel bar 50 presses too hard against the workpiece 12, it may crack or damage the workpiece. On the other hand, if the peel bar 50 does not press hard enough against the workpiece 12, the removal tape 30 will not laminate to the protective tape 18 with sufficient force to initiate removal of the protective tape. Accordingly, there is a need to improve the methods and systems for removing protective films from microfeature workpieces.